@juntoz/azure-function-logger-papertrail/index.js

Quick logger that enables the function to log to the default logger (console) and also to papertrail

const winston = require('winston');
require('winston-syslog');
var path = require('path');
var appDir = path.dirname(require.main.filename);

// singleton list that is shared across instances and can serve to avoid creating expensive logger every time
var _papertrailList = [];

class Logger {
    constructor(papertrailConfig, ctxLog, logLevel) {
        logLevel = logLevel || 'info';
        this.app_name = papertrailConfig.app ? papertrailConfig.app : appDir;

        // The papertrail logger will be static instance because it will be shared across all functions executions
        if (papertrailConfig.host) {
            if (!_papertrailList[this.app_name]) {
                _papertrailList[this.app_name] = winston.createLogger({
                    level: logLevel,
                    format: winston.format.json(),
                    transports: [
                        new winston.transports.Syslog({
                            host: papertrailConfig.host,
                            port: papertrailConfig.port,
                            app_name: this.app_name
                        })
                    ]
                });
            }
        }

        // The context logger lifetime is only for this function execution
        this._loggerThisCtx = winston.createLogger({
            level: logLevel,
            format: winston.format.json(),
            transports: [
                new _AzFuncCtxLoggerTransport({
                    ctxLog: ctxLog
                })
            ]
        });
    }

    end() {
        // NOTE: only end the local context logger, singleton papertrail logger must remain
        if (this._loggerThisCtx) {
            this._loggerThisCtx.end();
        }

        this._loggerThisCtx = null;
    }

    verbose(msg) {
        this.debug(msg);
    }

    debug(msg) {
        [_papertrailList[this.app_name], this._loggerThisCtx].forEach((l) => l && l.debug(msg));
    }

    info(msg) {
        [_papertrailList[this.app_name], this._loggerThisCtx].forEach((l) => l && l.info(msg));
    }

    warn(msg) {
        [_papertrailList[this.app_name], this._loggerThisCtx].forEach((l) => l && l.warn(msg));
    }

    error(msg) {
        [_papertrailList[this.app_name], this._loggerThisCtx].forEach((l) => l && l.error(msg));
    }
}

class _AzFuncCtxLoggerTransport extends require('winston-transport') {
    constructor(opts) {
        super(opts);
        this.ctxLog = opts.ctxLog;
    }

    log(info, callback) {
        switch(info.level) {
            case "verbose":
            case "debug":
                this.ctxLog.verbose(info.message);
                break;
            case "info":
                this.ctxLog.info(info.message);
                break;
            case "warn":
                this.ctxLog.warn(info.message);
                break;
            case "error":
                this.ctxLog.error(info.message);
                break;
        }

        this.emit('logged', info);

        // Perform the writing to the remote service
        callback();
    }
};

module.exports = Logger;